@article {Hansen:1 May 2008:0045-5067:1133, title = {Epidemiology of Phytophthora ramorum in Oregon tanoak forests}, journal = {Canadian Journal of Forest Research}, volume = {38}, year = {Submitted}, pages = {1133-1143(11)}, abstract = {

We followed the local intensification and dispersal of Phytophthora ramorum Werres, De Cock, \& Man In{\textquoteright}t Veld in Oregon tanoak (Lithocarpus densiflorus (Hook \& Arn.) Rehd.) forests from its initial detection in 2001 through 2006, coincident with a continuing eradication effort. The initial infested area included nine scattered sites below 400m elevation, close to the Pacific Ocean near Brookings, Oregon. In subsequent years, one-half of new infections were within 122m of a previous infection, and 79\% of the newly detected trees occurred within 300m of a previously identified tree. Dispersal up to 4km was occasionally recorded. Initial infection occurred in the upper crowns of tanoak trees. The pathogen was recovered in rainwater collected beneath diseased tanoak trees in every month from November 2006 through October 2007. Twenty-four multilocus microsatellite genotypes were identified among 272 P. ramorum isolates collected from Curry County. Genotypic analysis provided independent estimates of time of origin of the Oregon infestation, its clustered distribution, and dispersal distances. In all sampling years, 60\%-71\% of the isolates belonged to the same multilocus genotype. In 2001, 12 genotypes were detected and new genotypes were identified in each of the subsequent years, but all isolates belonged to the same clonal lineage. Knowledge of local intensification of the disease and long-distance dispersal should inform both Oregon eradication efforts and national quarantine regulations.

}, doi = {10.1139/X07-217}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/X07-217$\#$.UNIUO7aKS0c}, author = {Hansen, E.M. and Kanaskie, A. and Prospero, S and McWilliams, M. and Goheen, E. M. and Osterbauer, N. and P. Reeser and Sutton, W.} } @article {360, title = {Phytophthora nemorosa, a new species causing cankers and leaf blight of forest trees in California and Oregon, U.S.A.}, journal = {Mycotaxon}, volume = {88}, year = {2003}, pages = {129{\textendash}138}, abstract = {

Phytophthora nemorosa, a new species isolated from stem cankers on two species of Fagaceae and leaves of various hosts, is described. The new species resembles P. ilicis with homothallic, amphigynous antheridia and deciduous, semi-papillate sporangia, and has a related ITS-DNA sequence. Symptoms and host range are similar to P. ramorum, cause of Sudden Oak Death and leaf blight and shoot dieback diseases in California and Oregon forests, although P. nemorosa does not appear to cause wide-spread mortality of oak trees.

}, keywords = {Lithocarpus densiflorus, Phytophthora ilicis, Phytophthora ramorum, Quercus agrifolia, Umbellularia californica}, url = {http://www.mycotaxon.com/vol/abstracts/88/88-129.html}, author = {Hansen, E.M. and P. Reeser and J. M. Davidson and Garbelotto, M. and K. Ivors and L. Douhan and D. M. Rizzo} } @article {hansen1979isolation, title = {Isolation, incidence and management of Phytophthora in forest tree nurseries in the Pacific Northwest [USA]}, journal = {Plant Disease Reporter}, volume = {63}, year = {1979}, pages = {607-611}, issn = {0032-0811}, author = {Hansen, E.M. and P.B. Hamm and Julis, AJ and L.F. Roth} } @article {res2008alien, title = {Alien forest pathogens: Phytophthora species are changing world forests}, journal = {Boreal Env. Res.}, volume = {13}, year = {2008}, pages = {33{\textendash}41}, issn = {1797-2469}, author = {Hansen, E.M.} } @article {doi:10.1094/PD-89-0063, title = {Susceptibility of Oregon forest trees and shrubs to Phytophthora ramorum: a comparison of artificial inoculation and natural infection}, journal = {Plant Disease}, volume = {89}, number = {1}, year = {2005}, pages = {63-70}, abstract = {

Phytophthora ramorum is an invasive pathogen in some mixed-hardwood forests in California and southwestern Oregon, where it causes sudden oak death (SOD) on some members of Fagaceae, ramorum shoot dieback on some members of Ericaceae and conifers, and ramorum leaf blight on diverse hosts. We compared symptoms of P. ramorum infection resulting from four different artificial inoculation techniques with the symptoms of natural infection on 49 western forest trees and shrubs; 80\% proved susceptible to one degree or another. No single inoculation method predicted the full range of symptoms observed in the field, but whole plant dip came closest. Detached-leaf-dip inoculation provided a rapid assay and permitted a reasonable assessment of susceptibility to leaf blight. Both leaf age and inoculum dose affected detached-leaf assays. SOD and dieback hosts often developed limited leaf symptoms, although the pattern of midrib and petiole necrosis was distinctive. Stem-wound inoculation of seedlings correlated with field symptoms for several hosts. The results suggested that additional conifer species may be damaged in the field. Log inoculation provided a realistic test of susceptibility to SOD, but was cumbersome and subject to seasonal variability. Pacific rhododendron, salmonberry, cascara, and poison oak were confirmed as hosts by completing Koch{\textquoteright}s postulates. Douglas-fir was most susceptible to shoot dieback shortly after budburst, with infection occurring at the bud.

}, doi = {10.1094/PD-89-0063}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PD-89-0063}, author = {Hansen, E.M. and Parke, J. L. and Sutton, W.} } @article {361, title = {Species of the Phytophthora megasperma complex}, journal = {Mycologia,}, volume = {83}, year = {1991}, month = {May - Jun., 1991}, pages = {376-381}, issn = {00275514}, url = {http://www.jstor.org/stable/3759999}, author = {Hansen, E.M. and D. P. Maxwell} } @article {hansen1989testing, title = {Testing Port-Orford-cedar for resistance to Phytophthora.}, journal = {Plant Disease}, volume = {73}, number = {10}, year = {1989}, pages = {791{\textendash}794}, issn = {0191-2917}, author = {Hansen, E.M. and P.B. Hamm and L.F. Roth} } @article {doi:10.1094/PDIS.1999.83.6.587B, title = {First confirmation of Phytophthora lateralis in Europe}, journal = {Plant Disease}, volume = {83}, number = {6}, year = {1999}, pages = {587-587}, doi = {10.1094/PDIS.1999.83.6.587B}, url = {http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.1999.83.6.587B}, author = {Hansen, E.M. and Streito, Jean-Claude and Delatour, Claude} } @article {hansen1996survival, title = {Survival of Phytophthora lateralis in infected roots of Port Orford cedar}, journal = {Plant Disease}, volume = {80}, number = {9}, year = {1996}, pages = {1075{\textendash}1078}, publisher = {[St. Paul, Minn.: American Phytopathological Society], 1980-}, issn = {0191-2917}, author = {Hansen, E.M. and P.B. Hamm} } @article { refId, title = {Phytophthora species in oak forests of north-east France}, journal = {Ann. For. Sci.}, volume = {56}, number = {7}, year = {1999}, pages = {539-547}, abstract = {

Phytophthora species were surveyed from the end of 1997 through July 1998 in oak forests in NE France. Healthy (Amance) or declining (Illwald) forests were compared. The Phytophthora population in both was diverse and locally abundant. At least eight species were present at Amance and six at Illwald. At Amance Phytophthora species had a localized distribution in water and low-lying soils. At Illwald distribution was more uniform apparently due to flooding events. Most often recovered were P. citricola, P. gonapodyides and P. quercina. P. gonapodyides was ubiquitous in water and colonized leaf debris. P. quercina was widely distributed in soil but not abundant, and was found in sites that did not otherwise appear to favor Phytophthora. No correlation was detected between presence of Phytophthora in soil and health of trees. Unusual combinations of environmental factors may be required for resident Phytophthora to have a detrimental impact on oaks. {\textcopyright} 1999 Editions scientifiques et m{\'e}dicales Elsevier SAS.

}, doi = {10.1051/forest:19990702}, url = {http://dx.doi.org/10.1051/forest:19990702}, author = {Hansen, E.M. and Delatour, Claude} } @article {657, title = {Survival, spread, and pathogenicity of Phytophthora spp. on Douglas-fir seedlings planted on forest sites.}, journal = {Phytopathology 70:}, volume = {70}, year = {1980}, pages = {422-425}, abstract = {

Douglas-fir seedling stock infected in the nursery with Phytophthora cryptogea, P. drechsleri, P. megasperma, P. cactorum, and an unidentified Phytophthora sp. were outplanted on commercial forest sites to test survival of the diseased trees and of the pathogens. Mortality of trees initially classified in severe, moderate, and inconspicuous symptom classes at outplanting reached 61, 26, and 11\%, respectively, after 18 mo. Phytophthora was recovered about equally from roots of trees in each symptom class (15, 13, and 12\%). Surviving trees regenerated healthy roots above old lesions even though Phytophthora persisted. Disease spread was limited. None of 360 healthy trees planted 0.6 m downslope from diseased trees became infected, and only 2 of 720 healthy trees became infected after each was paired with a diseased tree in the same planting hole.

}, doi = {10.1094/Phyto-70-422}, url = {http://www.apsnet.org/publications/phytopathology/backissues/Documents/1980Abstracts/Phyto70_422.htm}, author = {Hansen, E.M. and L.F. Roth and P.B. Hamm and A. J. Julis.} } @article {Hansen1986557, title = {The taxonomic structure of Phytophthora megasperma: Evidence for emerging biological species groups}, journal = {Transactions of the British Mycological Society}, volume = {87}, number = {4}, year = {1986}, pages = {557 - 573}, abstract = {

Nomenclatural uncertainty surrounds P. megasperma as various authors, working with limited groups of isolates, offer their interpretations of this species based on pathology, morphology, or cytology. We compared 93 isolates, including many described by others, for classical morphological features, growth behaviour and appearance, electrophoretic pattern of total proteins, chromosome number and nuclear DNA content. Nine distinct sub-groups were distinguished. While most groups could be distinguished by each of the criteria, protein electrophoresis was the most sensitive. The groups included: ALF, pathogenic to alfalfa, n = 12{\textendash}15; SOY, pathogenic to soybean, n = 12{\textendash}15; CLO, pathogenic to clover, n = 11{\textendash}15; DF, pathogenic to Douglas fir, n = 17{\textendash}24; AC, isolated from rosaceous fruit trees; and BHR, a major group obtained from a broad range of hosts. The last two groups, distinguished primarily by protein pattern, comprised at least four karyotypes: KI, n = 12{\textendash}17; KII, n = 15{\textendash}23; KIII, n = 22{\textendash}28; and KIV, n= 26{\textendash}34. All four karyotypes occur within the BHR protein group, suggesting a polyploid series within a closely related genotype.

Two broad lines of evolution are hypothesized, a legume line comprising ALF, SOY, CLO, and perhaps DF isolates, and a Broad Host Range line of AC and BHR isolates. Sub-groups within each line may represent emerging biological species, isolated by host specificity or karyotype. Taxonomic designation for the various groups must await confirmation of the hypothesis by demonstration of the extent of barriers to gene flow between the groups.

}, issn = {0007-1536}, doi = {10.1016/S0007-1536(86)80097-3}, url = {http://www.sciencedirect.com/science/article/pii/S0007153686800973}, author = {Hansen, E.M. and C.M. Brasier and D.S. Shaw and P.B. Hamm} }